Purification of steel in the bessemer process



Patented Oct. 13, 1931 GHARLES HENNIG, OF CLEVELAND, OHIO PUB IFICA TION' OF STEEL IN THE BESSEMER PROCESS No Drawing.

' This invention relates to the manufacture of steel and more especially to the Bessemer process, whether acid or basic.

In the Bessemer process, as heretofore conducted, the resultant steel has not been entirely satisfactory, for many purposes, because of the fact that it carried a relatively large amount of iron oxide, manganese oxide and other impurities. Bessemer steel, as heretofore manufactured, has also been relatively high in nitrogen. These impurities have rendered Bessemer steel unsuitable for many uses, such as sheets for drawing purposes, certain grades of wire, and rails. In the steel trade, -Bessemer steel, as heretofore made, has been commonly designated as a dirty steel because of'the above mentioned impurities.

' The inclusion of oxides, in Bessemer steels as heretofore manufactured, has been the result of the action of the oxygen in the air used for the blow combining with the metal elements of the molten mass, since the air is disseminated throughout the molten mass and the oxygen contacts with practically every particle thereof. I For these reasons the manufacture of steel by the Bessemer process has been on the decline in this country for many years and its use has been restricted to certain products, such as pipes, bolts and other products requiring a free-cutting stock.

in the open-heart Another factor that has accelerated the' decline in the Bessemer process in this country has beefi'the development of the open-hearth process because of the possibility of using a g feater variety of materials process than in the Bes semer process. It is one of the objects of the present invention to improve theBessemer process so as to enable the production 'of cleaner steel a or. in other words, steel having a'lower content of dissolved oxides therein, which permits the use of such steel for a greater variety of products, because of its greater ductility.

Application filed August 16, 1929. Serial No. 386,490.

It is a further object of the inventionto improve the Bessemer process so as to enable the manufacture thereby of steels that are, generally speaking, equal to corresponding steels made by the open-hearth process and I have found that, in some instances, it is possible to make steels by my improved essemer'process that are superior to corresponding steels made by the open-hearth process. 1

The Bessemer process has many commercial advantages over the open-hearth process and among these advantages are the fact that a the steel can be made in a few minutes by the Bessemer process Whereas it takes many hours by the open-hearth process and that the process is more flexible in that many grades or analyses ofsteel may be made from the amount of metal that would be necessary for a heat in an open-hearthfurnace and, in I the case of an open-hearth furnace, all of the metal. of each heat would necessarily conform to a single specified analysis. In other words, the metalthat would be used to make a one hundred ton heat in-an openhearth furnace, all of which would be of one kind of steel to meet one specification, could by the'Bessemer process be made into any number of different kinds of steel depending I upon the size of converter used. I

It is common practice to use from two to twenty-five tons of molten metal in a blow, depending upon the equipment of the plant and the demand for the steel.

In carrying out'my invention, the molten metal from the blast furnace, cupola or mixer, is charged into the converter in the usual. way

- and the blow is made in the usual way and,

upon the completion of the blow, the metal is poured into the pouring ladle. .After a small amount .of the metal has been poured into thepouring ladle, I throw into the ladle a charge of purifying material, such as is dis closed in-my earlier application No. 301,434, filed August 22,1928 and which consists cs- 50 acts as a seal for the surface of the metal and Per cent Commercial soda ash (Na CO 80 Calcium oxide (CaO) as li1nestone 2 to 6 Manganese dioxide (MnO to 1 Chlorine, as calcium chloride (CaCl orsodium chloride (NaCl) The balance consists of a binder and impurities in the form of silica, magnesia, ironand alumina. The materials, in the proportions specified, are made up in the form of briquets and the binder that is used in these briquets is preferably glucose or molasses refuse, which is mixed with the other materials of the briquets', in a heated condition, and then run thro ugh a machine in which the mixture is pressed into briquet form. These briquets are preferably of a size that would Weigh about three ounces each.

The amount of briquets to be used varies with the quality of steel desired and may run from one-half to three pounds per ton of metal. The briquets are usually put into a paper bag and this bag is thrown into the ladle while the metal is being poured into it from the converter and should be put in prior to the time that the manganese is added, because the purifier tends to protect the manganese against oxidation and, therefore, permits of the use of a smaller amount of manganese than has heretofore been the practice.

The addition of the purifier results in an immediate and energetic ebullition of the metal which carries the included gases and impurities to the top where the impurities are held by the slag and the gases pass out through the slag and are entirely eliminated. The action of the purifier lasts for about a minute and then the metal is thoroughly degasified and cleansed of the oxides and other impurities which it originally contained. The resultant slag is liquid and very quiet and the-fact that the slag is quiet indicates that the metal has been thoroughly degasified. The metal is then ready for pouring into the molds.

If the metal is over-oxidized in the blow and has a tendency to not liequietly in the first mold, some of the purifier may be added to each of the other molds, either on the stool or during the pouring, and this will result in the metal lying quietly in the molds. For this purpose, about one-fourth of an ounce to one ounce per ton of metal should be added to each mold.

If the metal from the blast furnace, cupola pending upon the appearance of the metal, it

being understood that those skilled in the art are able to detect the condition referred to from the appearance of the metal and by such appearance will be able to determine the amount of the purifier that is to be used in any case. Vhen the purifier is put into the transfer ladle,'it acts on the metal in the ladle and the metal with the slag containing I the purifier is then poured into the converter where the purifier continues its action. In some cases the purifier may also be put into the converter where the condition of the metal is unusually bad or, if preferred, in some cases, the purifier may be put in the converter and not in the transfer ladle. When the purifier is put into the converter, it is preferable to do this either before the metal is run in or beforethe blow starts.

Having thus described my invention, what I claim is: v

1. The hereindescribed method of purifying steel in the Bessemer process of manufacture which consists in treating the molten metal, after it has been blown, with a deoxidizing material in the form of an intimate mixture comprising commercial soda ash and manganese dioxide and wherein the soda ash is over three-fourths of the mixture and the manganese dioxide is an'eifective amount, up to five per cent, for controlling the action of the soda ash as and for the purpose described.

2. The hereindescribed method of purifying steel in the Bessemer process of manufacture which consists in treating the molten metal, after it has been blown, with a deoxithe manganese dioxide is an effective amount,

up to five per cent, for controlling the action of the soda ash as and for the purpose described.

3. The hereindescribed method of purifying steel in the Bessemer process of manufacture which consists in treating the molten metal, after it has been blown, with lumps of a deoxidi'zing material in the form of an intimate mixture comprising commercial soda ash, a calcium compound, and manganese dioxide, and wherein the soda ash is over threefourths of the mixture, the calcium compound has'a calcium oxide content that is an effective amount, up to ten per cent, to substantially raise the meltin point of the soda ash,

and the manganese ioxide is an efiective amount, up to five per cent, for controlling a the action of the soda ash as and for the purpose described.

In testimony whereof, I hereunto aflix my signature.

CHARLES T. HENNIG; 

